1. Field of the Invention
The present invention relates to an optical writing apparatus and an image forming apparatus.
2. Description of the Related Art
Among various types of image forming apparatuses including a printer, a copier, a facsimile machine, and a multi-functional apparatus having multiple functions, there is, for example, a tandem type color image forming apparatus. Multi-colored images are formed with this image forming apparatus, for example, by recording latent images onto an arrangement of four image carriers (e.g. photoconductor drums) by irradiating light beams from multiple light sources thereto, developing (and making visible) the latent images on the image carriers by using developers of different colors (e.g. toners of yellow, magenta, cyan, and black), successively conveying transfer materials (e.g. recording paper) on a transfer conveyor belt to transfer portions corresponding to respective latent images, superposing and transferring the developed visible images to the transfer materials, and fixing the transferred images onto the transferred materials.
One example of an optical writing apparatus used for the tandem type color image forming apparatus is shown in Japanese Laid-Open Patent Application No. 2002-196269. This optical writing apparatus includes multiple light sources, a light deflecting part for deflecting the multiple light beams from the multiple light sources to two opposite directions, and optical systems symmetrically disposed in two directions with the light deflecting part situated at the center for forming images by scanning the multiple light beams (deflected by the light deflecting part) to a target scanning plane, in which the multiple light sources, the light deflecting part and the optical systems are installed in a single housing.
Another example of an optical writing apparatus used for the tandem type color image forming apparatus is shown in Japanese Laid-Open Patent Application No. 10-148777. This optical writing apparatus deflects multiple light beams irradiated from multiple light sources by using a light deflecting part having deflecting planes. This optical writing apparatus includes multiple imaging parts corresponding to the multiple light beams for imaging onto a photoconductor(s). The multiple imaging parts is integrally formed with light forming elements (fθ lenses) that are overlappingly layered in a sub-scanning direction. Furthermore, the image forming elements are provided with reflection planes with a converging property (converging function). The optical writing apparatus allows multiple light beams to be incident on a synchronization detection part for obtaining synchronicity.
Nevertheless, with the technology shown in Japanese Laid-Open Patent Application No. 10-148777, in order to guide multiple light beams to the same synchronization detection part, the reflections planes that are to be mounted on the imaging elements (fθ lenses) require a converging property (converging function). This, however, causes the configuration of the image forming element to be complicated.